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HSRP

Hi all, I would like to know what Cisco says is the ideal way to set up redundant WAN links and do load balancing also.

4 REPLIES

Re: HSRP

HSRP does not do load balancing. Try looking into GLBP (Gateway Load Balancing Protocol). Has the features of HSRP and the ability to load balance. See here:

http://www.cisco.com/en/US/customer/products/sw/iosswrel/ps1839/products_feature_guide09186a00801541c8.html

Silver

Re: HSRP

Neither is appropriate for WAN links, as they only work on broadcast media such as Ethernet. Try reposting your question under a more appropriate title, such as T1 load balancing (or whatever WAN links you are using, the answer will vary significantly depending if the media is DS1, DS3, OC3, SONET, LD Ethernet, etc.) Also critical is relative importance TO YOU of availability versus cost versus eveness/fairness of load balancing.

Good luck and good hunting!

Vincent C Jones

www.networkingunlimited.com

Re: HSRP

Sorry, I really have to question that last post. HSRP and GLBP are very appropriate for WAN links. Yes, they actually do their work on an ethernet segment by creating a shared MAC-address/IP Address so two or more routers can share a default-gateway between them, but the reason most people use them is to share a default-gateway between two routers connected to a WAN link...

There is actually another nice article I'd like to quote from on Cisco's site: "There are two spots in the network where the use of GLBP is highly recommended: in the campus network, in an aggregation gateway where the Layer 2 switched access layer meets the Layer 3 routed layer (see figure); and at the WAN edge of remote sites, where dual- or multi-homed connections are in place for high availability networking."

http://www.cisco.com/en/US/customer/about/ac123/ac114/ac173/ac253/about_cisco_packet_enterprise_solution0900aecd800e015a.html

Why do you say that they aren't appropriate for WAN links?

Silver

Re: HSRP

By itself, HSRP/GLBP does not provide higher availability of redundant WAN links (the key feature request in the original poster's question). WAN link load balancing is a side effect of HSRP/GLBP only in a very limited scenario where the source of traffic is from multiple local systems on the same LAN segment as both gateway routers and the choice of default gateway has the side effect of selecting one WAN link over another. There is no scenario where HSRP/GLBP provides load balancing for inbound traffic from the WAN.

Depending upon the specific connectivity scenario, the appropriate solution for higher availability could include keepalives, frame-relay end-to-end keepalives, EIGRP, OSPF, RIP, RIPv2, floating static routes, BGP, policy routing on reachability, etc., and appropriate solutions for load balancing could include CEF per packet, CEF per flow, MLPPP, BGP AS path padding, creative IP subsetting, EIGRP variance, policy routing, etc.

You are correct that HSRP/GLBP may have a place in a design with WAN links (and, indeed, I give an example of exactly that usage in my book High Availability Networking with Cisco). But to call it a solution for the problem asked is giving it too much credit, and could contribute to the common misconception that HSRP/GLBP is a substitute for a routing protocol rather than a mechanism to get around the shortcomings of IP's default gateway limitations on a LAN with multiple routers present.

Vincent C Jones

www.networkingunlimited.com

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